The present invention relates to a rotary valve for controlling the discharge of molten metal in a substantially downward or vertical direction from a metallurgical vessel, the rotary valve including a refractory rotor to be rotatable about a substantially horizontal axis within a refractory stator having a discharge channel, wherein the rotor has a flow channel to be moved into and out of alignment with the discharge channel upon the rotation of the rotor about the axis. The present invention also relates to a refractory rotor and to a refractory stator employable in such rotary valve.
A rotary valve disclosed in FIG. 1 of DE-PS 33 42 836 is partially installed in a cavity of the refractory lining of the bottom of a metallurgical vessel. The cavity is lined with a refractory housing formed by refractory shaped bricks and a cored panel into which the rotary valve is inserted and partially grouted therein. When the rotary valve is repaired, the refractory housing also must be repaired, and this is a difficult task. Additionally, the housing forms on the one hand a thermal insulating shield to the molten metal, and the rotary valve is subjected to air cooling, thereby providing a substantial risk of the rotary valve freezing. Such risk of freezing is even greater with the rotary valve shown in FIG. 3 of such reference, since the function of this rotary valve is to close a pipeline. Additionally, the rotor is not replaceable without replacing the stator.
In a rotary valve disclosed in DE-PS 33 06 670, tapping is achieved horizontally so that the rotor has to be designed as a relatively long valve member having a through bore with a discharge port and projecting sideways horizontally out of a vessel bottom. Thus, short pouring paths cannot be achieved, and there is a high risk of freezing. Also, since the valve member is made of a refractory material and has therethrough an axial bore, it is not possible to transfer to the rotor sufficient torque, when the rotor is tightly seated against a stator, to rotate the rotor, when the rotor and stator are subjected to thermal expansion. Further, the rotor has relatively thin walls as a result of which the rotor is susceptible to wearing out rapidly.
Disclosed in DE-AN 36 43 718 is a rotary slide valve including a perforated brick, an entry nozzle, a closing plate and a refractory discharge pipe with the plate-like flange. These elements also are arranged relatively far from the molten metal, thereby additionally increasing the risk of freezing.
A problem involved with the rotary valve disclosed in DE-OS 26 08 472 is that conical surfaces of a rotor and stator must have a high precision of fit to allow easy rotation of the rotor within the stator and to ensure a good seal therebetween. Also, the rotor suffers from tensile loading. Additionally, the rotor cannot be replaced through the vessel bottom or the vessel side wall without the stator. In operation, the rotor normally is subjected to higher wear than the stator so that it must be replaced more often than the stator. The geometry of the stator and rotor also require that the rotary valve is arranged and thus actuated in the immediate vicinity of the pouring stream, that is a region of very high temperatures. The entry port of the flow channel through the rotor is configured in a face thereof that is spherical. This results in the rotor wearing out very rapidly, particularly in a corner region in the immediate vicinity of the flow channel.
Disclosed in AT-PS 357 283 is a rotary valve arranged in a vessel bottom, particularly in a manner such that the rotor cannot be replaced through the vessel bottom without also replacing the stator. The rotor suffers from tensile loading and can be actuated only from the bottom of the vessel.
A rotary valve disclosed in AT-PS 165 292 is located primarily outside a cavity of a vessel, particularly below the vessel bottom. Therefore, the risk of freezing is relatively high, and the actuating assembly for the valve is located relatively near the pouring stream. Due to the construction involved, the rotor can be replaced only with the stator and can be actuated only from below since the axis of rotation is vertical.
An outlet valve disclosed in GB-PS 2 174 029 includes a stator mounted in the lining of the base of a vessel, with an upper portion of the valve projecting through the entire molten metal bath in the vessel to a supporting arm above the vessel. This requires a substantial cost of construction. Additionally, the rotor and stator must be closely complementary. Furthermore, the contact pressure must be actuated via the bearing arm. Still further, only faces of the rotor and stator make contact, and this can result in both guiding and sealing problems.
A rotary valve disclosed in GB-PS 1 177 262 is not positioned in or on the lining of a wall of the vessel, but rather is actuated from below the vessel bottom. The rotor has a flow channel configured in a relatively complicated shape and thus is subject to rapid deterioration. Also, the rotor cannot be replaced through the vessel bottom without the stator, but rather both the rotor and stator are replaced from the interior of the vessel.
Disclosed in U.S. Pat. No. 3,651,998 is a rotary valve primarily in the form of two cylindrical mating pipes with a vertical axis and that extend through a vessel bottom. The pipes have a special sealing arrangement. Actuation is in the immediately vicinity of the pouring stream. The pipes have relatively thin walls and therefore are subject to rapid wear.
A feed control element for controlling the filling level of a continuous casting plant is disclosed in DE-PS 35 40 202. At least two movable, concentrically arranged, vertically extending pipes pass into a supply vessel and have break-throughs for the passage of the melt to prevent occlusion of a discharge port of a melt storage container. The break-throughs can be brought more or less into alignment by adjusting at least one pipe from above. The other pipe can be axially adjusted and rotated with respect to the one pipe. The actuation arrangement is relatively complicated and must be operated from above the metal melt. The replacement of parts is difficult, and this is a particular drawback since the parts are subject to rapid wear.
A device for controlling the flow rate from a tundish for continuous pouring is disclosed in Japanese application 61 182 857, the device having, for the purposes of reducing oxidation of a steel melt and improving the quality of the steel, a stator permanently mounted in a vessel bottom, and a vertical discharge channel into which lateral discharge ports open at small intervals above the vessel bottom. The discharge rate is conducted with the aid of a vertical ram that is guided in the discharge channel of the stator and that is actuated for vertical adjustment from above the metal melt. Instead of the ram, a tubular valve member, similar to that disclosed in DE-PS 35 40 202, also can be used. This valve device requires actuation from above the metal melt. Also, the parts subject to wear, i.e. the rotor and stator, can be replaced only from above the vessel.
A device for controlling the discharge of molten metal from a vessel disclosed in CH-PS 571 374 includes a valve member actuated from below a vessel bottom and guided adjustably vertically in a stator of the vessel bottom. The valve member has a vertical flow channel which divides into two cross bores toward the top. In an open position, entry ports of such cross bores are above the surface of the vessel bottom within the metal melt. When the valve member is in a closed position, the entry ports are within a rotor. Actuation is achieved from below the vessel bottom, and thus in the immediate vicinity of the pouring stream.
In a rotary valve disclosed in GB-PS 183 241, a stator and rotor are arranged substantially below the vessel bottom, so that there is a significant risk of freezing of the metal melt. Furthermore, the rotor has an axis of rotation that is perpendicular to a vertical discharge channel of the stator and a flow channel extending perpendicular to such axis of rotation. Thus, the rotor must be actuated in the immediate vicinity of the pouring stream below the vessel bottom.